Harvesting Coffee

Coffee is usually harvested between September and March north of the equator, and between April and May south of the equator. Although some arabica shrubs are harvested selectively (meaning the cherries will be hand-picked only when ripe), it’s much more common for all of the cherries on one branch, ripe or unripe, to be stripped all at once. After picking, the cherries must be processed immediately. They can either be dry-processed or wet-processed.

Dry-processing is the older and simpler method of the two. Coffee cherries are dried, usually in the sun on specially-constructed surfaces or raised terraces (sometimes machine drying is part of this process). The cherries are periodically turned or raked during the drying process, which can take up to four weeks. Once the cherries are dried, the entire outer hull can be removed from the beans at once.

Wet processing involves water, as might be suspected, and a great deal of it. This is the typical processing method for Arabica coffee; most robusta is dry-processed. “Green” (that is, unroasted) coffee beans that are products of wet-processing are usually thought to be of higher quality than dry-processed beans. Wet-processing involves separating the beans from the rest of the cherry before drying. In progressive stages, much of the coffee cherry’s skin and pulp are removed from the beans by machinery and washings. However, some pulp, as well as a sticky, almost gelatinous layer, will still adhere to the beans afterward. This is removed by fermentation, accomplished with the use of enzymes, followed by more washing.

Drying is then done in the sun or by machine. Although it is beyond the scope of this article, wet-processing (also called wet-milling) was a major source of resource waste and pollution for many years and in numerous countries. Wet-processing requires large amounts of water and creates vast quantities of oxygen-depriving coffee waste, which was often dumped, untreated, on land or into water, causing tremendous river/stream pollution, including expanding “dead zones.” In the late 1990s, governments of countries affected by such stream pollution began to demand clean-ups of this part of the coffee industry. Among other measures, water use was to be minimized; coffee waste was to be composted or turned into biogas, a fuel produced by the activity of anaerobic bacteria.

The proper drying of coffee beans is considered an important step in their processing. Overdrying will result in broken beans, considered inferior. Once beans are dried, they are graded, and eventually, bagged and shipped. Coffee beans are shipped “green” and roasted to the degree desired by the purchaser.